Power plant



Aug. 23, 1938. A E P 2,127,602

POWER PLANT Filed July 51, 1957 l I I6 GEORGE A. JESSOP By WM @M Patented Aug. 23, 1938 PATENT OFFICE i POWER PLANT George A. Jessop, York, Pa assignor to S. Morgan Smith Company, York, Pa.., a corporation of Pennsylvania Application July 31, 1931, Serial No. 156,619

4 Claims 115-355) This invention relates to centrifugal machines, and more particularly to means for reducing the runaway speed of centrifugal machines.

An object of the invention is to provide improved means for controlling the operation of centrifugal machines, especially units composed of a prime-mover and an electric generator, so as to reduce the overspeed of such units when they lose their commercial power load and their power controlling equipment fails to operate to cut oil? the energy from the prime mover.

Another object of the invention is to provide improved runaway speed reducing means of the above type, in which the centrifugal machines are controlled by electrically operated control apparatus.

With the foregoing and other objects and advantages in view, the invention consists in the construction and arrangement of the several parts which will be more fully described and claimed.

In the accompanying drawing, the single figure is an elevation partly in vertical section of a Well-known type ofhydraulic turbine installation, embodying the present invention.

The over-speed or no-load speed of some types of centrifugal machines, such as hydraulic turhines, is sometimes very high. This is particularly true in the case of hydraulic turbines of the type having runners with movable or adjustable blades, and also, although to somewhat less degree, to hydraulic turbines having runners with fixed blades.

The runner of a hydraulic turbine, in general, is of sufficient strength to withstand the natural or full overload. In the case of hydraulic turbines having adjustable blade runners, however, the design of the thrust disk or bearing and the thrust collar to take the centrifugal load of each blade,. can be reducedin cost if the runaway speed can be safely limited.

The cost of an electric generator with which a hydraulic turbine is usually connected, can be substantially reduced if the runaway speed is re- 5 iduced. In the case where hydraulic turbines of the adjustable blade runner type are used to drive electric generators, the cost of the generators, due to the excessively high overspeed, is frequently very much higher than the cost of similar installations using other types of hydraulic turbines.

llhe invention is also valuable for use with many other types of centrifugal machines, as it provides a reliable, convenient means for reduc ing the. over-speed of such machines.

For instance, the invention can be used in connection with steam turbine units, since such units also have an excessively high runaway speed. In fact, the overspeed of steam turbines is so great that it is necessary to use special shutdown devices, so that when a certain percentage of overspeed is reached, steam is shut off from the unit.

The invention can be used wherever there is a body of quiet water, or where water for cooling is available, or a special tank containing water can be provided.

The invention can also be used with any kind of electrical power absorbing resistance, such as a rheostat. V

Prime movers are nearly always supplied with controlling means for shutting off the water, steam or other source of energy. The prime movers are usually so constructed that, if they suddenly lose their load due to electrical disturbances or otherwise, they will automatically shut down. For safety, provision must be made, however, that if the equipment fails to work from accidental or other causes, it will withstand the stresses set up by the abnormally high rotational .speed reached. 0r sometimes, because of adverse conditions imposed upon the equipment, the controlling apparatus must be shut down very slowly, thus allowing an abnormally high overspeed to be reached when the load is lost suddenly.

Referring to the drawing, the hydraulic turbine indicated at i l, is supplied with water from a fiume l2. The water, in passing through the turbine ll, flows through a draft or suction tube l3, and discharges in the usual tailrace it.

The turbine ll has a shaft I5 which is connected to the shaft iii of an electric generator l'l, so that the generator is operated by the turbine in well-known manner.

The waterpassing into the turbine II, is controlled by means of a governor l8 which is operatively connected to the wicket gates IQ of the turbine in the usual well-known manner.

If the turbine ii is operating and producing energy in the generator l1 and the load is suddenly lost, and if the governor it or the control mechanism fails so that the energy continues to be supplied to the turbine ll, an overspeed will be reached. In the case of an impulse wheel, a Francis or fixed blade propeller turbine, maximum overspeed is obtainedwith maximum supply of energy, that is at wide open position of the means controlling the supply of water. In the case of the adjustable blade type of turbines, maximum overspeed occurs with the gates in wide openpolition but-with thebladesin apartially open position.

According to the present invention, it is proposed to provide means which will automatically throw a substantial load on the generator l'l when a predetermined overspeed is reached.

weratively connected to the shaft ll of the generator i1 is a centrifugal switch device 2|. The switch device 22 can be directly mounted on the end of shaft II, or said switch device can be operated by gears or belts or other suitable mechanism from any convenient part of said generator shaft.

The centrifugal switch device 20 comprises a rotating or centrifugal element 2| which is mounted on the generator shaft it, a finger or plunger 22 which operatively engages the rotating or centrifugal element 2 I, and an electrical switch or contact a.

centrifugal switch devices of this type are well knownintheartandcanbepurchased inthe open market from manufacturers of electrical controlling equipment. a

When the overspeed of the turbine ii reaches a certain predetermined number of revolutions for which the switch device 20 is set, the centrifugal element 2| causes the finger or plunger 22 to make a contact or to close the switch 22.

The switch member 22 is electrically connected to a power switch device 24 by means of electric conductors 2. so that when the electric switch 23 operates in the above described manner, the power switch device 24 will be actuated. The power switch device is well-known in the art, and is readily obtainable from manufacturers of electrical controlling apparatus.

Immersed in the water in the fiume I2 is a rheostat 20 which is operatively connected with the power switch device 24.

The generator shaft ll carries collector rings 21 which are connected to the electric generator I! by conductor 2|.

operatively associated with the collector rings 21 are brushes 22 which are electrically connected to the power switch device 24 by conductors 20.

Leading from power switch device 24 are the power line conductors 2 I.

Connected to the switch contact member 22 of th'- centrifugal switch device 20, are conductors 32 for supplying electric current to said switch from a suitable source of electric current supply, such as a storage battery 22. a

In operation, when the load goes oil, the overspeed of the device becomes very high and consequently the centrifugal switch device 20 is operated by the rapidly rotating generator shaft l6 whereby centrifugal element 2| operatively engages finger or plunger 22 with contact 22. In this way, electric current supplied to the switch device 20 by conductors 22 is carried to the power switch device 24 by conductors 25 and the power switch operated to close its switch element 24. With the element 24 of the power switch 24 thus closed, electric current from the generator i1 will pass from the power switch device downwardly to the rheostat 26 and is carried off into the water in the fiume l2.

when normal load conditions return to the turbine and generator, the generator shaft It will slow down and when rotating at approximately its predetermined normal revolutions per minute, the centrifugal switch device 2| will open thereby opening the power switch device 2|, so that electric current from the generator I! is again supplied to the main power line conductors 2|.

Having thus described my invention, what I claim is:

1. A power plant comprising an electric generator, a hydraulic turbine for operating said generator and having a fiume containing operating fluid therefor, a main power line connected to said generator for conducting electric energy produced by the generator, and a rheostat immersed in the operating fluid in the fiume of the hydraulic turbine and adapted to be electrically connected with said generator when the operating speed of the generator exceeds a predetermined number of revolutions per minute for dispersing electric energy from said generator into the operating fluid in said fiume.

2. A power plant comprising an electric generator, a hydraulic turbine for operating said generator and having a fiume containing operating fiuid therefor, main power lines connected to said generator for conducting electric energy produced by the generator, a rheostat immersed in the operating fiuid of the hydraulic turbine time and adapted to absorb electric ener y. End electric switch means operable by variations in the speed of rotation of said generator and adapted to electrically connect the rheostat with the generator and to disconnect said generator from the main power lines when the speed of rotation of the generator exceeds a predetermined amount.

3. A power plant comprising an electric generator, a hydraulic turbine for operating said generator and having a fiume containing operating fiuid therefor, a centrifugal switch device operatively connected to the shaft of said'generator, said centrifugal switch device being normally open and being adapted to automatically close when the speed of rotation of the generator shaft exceeds a predetermined amount, main power lines for conducting electric energy produced by the generator, a rheostat immersed in the operating fluid of the hydraulic turbine flume and adapted to absorb electric energy, a power switch device operatively connected to said centrifugal switch device and adapted to control the electric current from said generator to said main power lines and to said rheostat, and a source of supply of electric energy connected to said centrifugal switch device and adapted to be supplied to said power switch device for operating the same when said centrifugal switch device is closed.

4. A power plant comprising an electric generator, a hydraulic turbine for operating said generator and having a fiume-containing operating fluid therefor, a main power line connected to said generator for conducting electric energy produced by the generator, and a rheostat immersed in the operating fiuid in the fiume of the hydraulic turbine and adapted to be electrically connected with said generator when the operating speed of the generator exceeds a predetermined number of revolutions per minute for absorbing electric energy from said generator.

GEORGE A. JESSOP. 

